Effects Of Ratio Of Wasp To Host Egg And Exposure Time On Quality Of Trichogramma

Quality of Trichogramma spp.is often affected by ratio of wasp tohost eggs and exposure time during parasitization.Different ratio of wasp tohost eggs and exposure timehave different effects on the parasitism rate,emergence rate,emerged female proportion,eggs load of Trichogramma.When the ratio of wasp tohost egg and exposure time is not suitable,heavy superparasitism would occur.The superparasitism effects on the quality of Trichogramma,and the deeper the superparasitism,the greater the negative impact on Trichogramma.The quality of Trichogramma is a key factor in its effective control of pests in the field.Trichogramma often faces superparasitism conditions during factory breeding,resulting in a decline in the quality of Ti-ichogramma,which affects the control of pests.At the same time,different Trichogramma species also differed in the ratio of wasp tohost eggs and exposure time.Breeding of Trichogramma japonicum,Trichogramma cacoeciae and Trichogramma chilonis with eggs of Corcyra cephalonica for factitioushost eggs,effect of different ratio of wasp tohost eggs and exposure time on its propagation was studied in the laboratory.The results are given as follows.1.Ratio of wasp tohost eggs and exposure timehad significant effect on breeding of T.japonicum.The parasitism rate increased first and then decreased with the increase of the number ofhost eggs.When the number ofhost eggs was less than or equal to 80,it will decreased with the increase of exposure time.When the number ofhost eggs was more than 80,it increased with the increase of exposure time.Emerged female proportion,eggs load andhind tibia length increased with the number ofhost eggs,and the number ofhost eggs less than 80 was significantly lower than the number ofhost eggs more than or equal to 80;Number of emerged wasp number per eggs and number of residual wasps decreased as the number ofhost eggs increased,and increased with the increase of exposure time,and it was significantlyhigher in treatment that thehost egg number was less than 80 than that in the treatment that thehost egg number was more than or equal to 80;The parasitism rate reached thehighest when the ratio of wasp tohost eggs was 3:80 and exposure time was 3hours.Therefore,this condition is the best for breeding Trichogramma with eggs of Corcyra cephalonica.2.When ratio of wasp tohost eggs was 3:40,parasitism was thehighest for T.cacoeciae.Followed by 3:60,which was reduced in turn.However,when the ratio ofhost eggs was 3:40,in addition to thehigh parasitism rate,emergence rate,eggs load andhind tibia length both were significantly lower that in those levels.Emerged wasp number per eggs and residual number was significantlyhigher than those in other levels.When the number ofhost eggs was more than or equal to 60,there were basically no significant difference between the treatments.Therefore,for breeding of T.cacoeciae the optimal wasp tohost eggs and exposure time was 3:60 and 3h,respectively.3.When ratio of wasp tohost eggs was 3:40,parasitism,emergence rate,eggs load andhind tibia length was significantly lower than other ratios.Emerged wasp number per eggs washighest in ratio of 3:40 with 9h of esposure time.The eggs load increased significantly with the increase of the number ofhost eggs.And the optimal proportion andhours was 3:120 and 9h,in which the index was significantlyhigher than other combinations.Therefore,suitable ratio of wasp tohost eggs and exposure time is 3:120 and 9h,respectiveiy.4.The quality of the three species of Trichogramma was different in the same ratio of wasp tohost eggs and exposure time.Parasitism and eggs load of T.japonicum is thehighest amount,followed by T.chilonis.The parasitism and eggs load of T.cacoeciae is significantly lower than the others,emergence rate andhind tibia length is significantlyhigher than the others.The emerged wasp number per eggs was the most abundant in the T.chilonis,followed by the T.cacoeciae,and it was the least for T.japonicum.The results indicated that wasp tohost eggs and exposure timehad significant effect on performance of Trichogramma.Different Trichogrammahave different requirements for ratio of wasp tohost eggs and exposure time.This experiment identified the best ratio of wasp tohost eggs and exposure time of three species of Trichogramma in the laboratory,which provided a theoretical basis for the industrial production.